Abstract | ||
USING COHERENT FIBEROPTIC CABLES TO PRODUCE HOLLOW BEAMS
When a laser beam is passed through a coherent fiber optic cable at an
angle to the axis of the cable, a hollow beam (or ring) is formed. The
diameter of this beam is proportional to the angle that the laser makes with
the cable. Hollow beams are used in atom trapping instead of a traditional
laser beam, so the atoms are in a dark spot and will not interact with the
photons. Hollow beams are typically produced by using Axicon lenses, but
Axicon lenses are expensive and fragile to use. I am trying to see if
fiber-optic cables can replace Axicons in producing hollow beams. I have been
using a photo detector to measure the light intensity profile using a 632.8
He-Ne laser, which I have found to be Lorentzian, not Gaussian (as I
expected), like the original laser beam. Also, the ring is not polarized,
unlike the original laser beam. The procedure I used was to first pass the
laser light through a 3mm hole (not pinhole or there would be diffraction),
then into the center of the fiber optic cable and then onto a screen. Because
of the way the laser box is built, it was not possible to accurately
determine the angle from where the laser starts, because I do not accurately
know where the tip of the laser is. My procedure allowed me to measure the
angle from the hole to the cable accurately. My results appear to show that
fiber optic cables can be used to produce hollow beams in place of Axicon
lenses. I would like to do further research with various fiber optic cables
and different lasers to confirm this.
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